The invention relates to an expansible plug to be percussion anchored in a borehole that tapers outward at an inner end thereof.
Expansible plugs of the kind mentioned above are known. Such an expansible plug is anchored in a borehole, a widened end of which forms an undercut in the region of the bore bottom, by driving an expander bolt into an expansible sleeve of the expansible plug.
An expansible plug to be percussion anchored in a borehole with an undercut is disclosed in DE-OS 30 20 907. An expansible plug to be anchored in a borehole with an undercut has to be expanded to a greater degree than an expansible plug anchorable in a cylindrical borehole. To provide for greater expansion of the expansible plug anchorable in a borehole with an undercut, the front end of the expander bolt which is opposite to the bolt end subjected to percussions, is rounded, and the neck portion of the borehole is provided with a very marked taper. Up to now known solutions of anchoring of expansible plugs in boreholes with an undercut often failed to insure a reliable conical fixation because the expansible plug became fixed in the bottom of the borehole and could not, therefore, expand. An optimal anchoring of the expansible plug in a borehole with an undercut could only be achieved by providing an expansible plug the expandable portion of which forms a form-locking fixation with the borehole undercut upon expansion of the plug.